Balloon angioplasty is a widely used procedure for expanding constricted body passageways, such as arteries and other blood vessels. In an angioplasty procedure, an un-inflated balloon attached to a catheter is delivered to a constricted region of a body passageway. Once the balloon is in position at the constricted region, fluid is injected through a lumen of the catheter and into the balloon. The balloon consequently inflates and exerts pressure against the constricted region to expand the passageway. After use, the balloon is collapsed, and the catheter is withdrawn.
Balloons have a number of critical design parameters. One is rated burst pressure, which is the statistically-determined maximum pressure to which a balloon may be inflated without rupturing. In order to expand hard, calcified lesions, it is desirable that the balloon have a relatively high rated burst pressure. It is also desirable that the balloon have a low wall thickness to minimize the profile of the delivery system when the balloon is in a deflated state. For a given balloon material, however, there is a trade-off between burst pressure and wall thickness, in that the burst pressure generally decreases when the wall thickness is reduced.
Accordingly, there is a need for increasing the strength of a balloon to attain a higher rated burst pressure while maintaining a low delivery profile.
Balloons used for stent delivery have the added requirement of delivering a stent in a controlled manner. Balloons with a large difference in their deflated profile (deflated diameter) and their expanded profile (expanded diameter) commonly inflate in an uneven manner along the length of the balloon. By way of example, one end of the balloon may attain an expanded diameter prior to the opposing end, or the middle of the balloon may expand prior to the ends. This inconsistency of inflation increases the likelihood that the stent will be dislodged longitudinally along the length of the balloon moving either partially or fully off the balloon. The inconsistency of inflation profile increases the likelihood for vessel trauma as the stent is unevenly expanded and subsequently unevenly engages the vessel wall.
Accordingly, there is a need in the art for a balloon system that provides for the control of the inflation profile to provide a uniform profile along the length of the balloon as the system is inflated to reduce the risk of stent misalignment/dislodgement and vessel trauma.
Doctors are also commonly faced with a decision pertaining to what diameter stent/balloon system to choose for delivery. Accuracy in measurement technique and the choices in device diameter often limit the doctor's ability to choose a balloon/stent system that is optimally sized for the intended vasculature.
Accordingly, there is a need for a balloon that provides one or more intermediate inflated diameters that are apparent to the doctor during delivery that provides a uniform profile (that is, a relatively uniform diameter) along the length of the balloon at each intermediate diameter.